1. Field of the Invention
One disclosed aspect of the embodiments relates to a measuring apparatus, an imprint system, a measuring method, and a device manufacturing method that measure the thickness of a residual layer of a pattern formed on a substrate.
2. Description of the Related Art
An imprint technique is a technique for, in the state where an imprint material (resin) supplied onto a substrate (a wafer) is brought into contact with a mold on which a pattern has been formed, curing the resin to form the pattern in the resin on the wafer.
In the imprint technique, after the pattern has been formed on the substrate, a thin resin layer called a “residual layer” remains. This requires the step of removing the residual layer by etching. In the step of removing the residual layer, also the pattern formed in the resin is etched together with the residual layer. The etching should not be performed more than necessary so that the pattern formed in the resin is influenced as little as possible. To that end, it is necessary to accurately measure the thickness of the residual layer.
As a method of measuring the thickness of a residual layer, scatterometry is known. Scatterometry is a technique for measuring the shape of a pattern by applying an optical simulation of the reflected light from a structural birefringent body. Such a method of measuring the shape of a pattern using scatterometry is described in Japanese Patent Application Laid-Open No. 2007-311469 and Japanese Patent Application Laid-Open No. 2009-162494.
Scatterometry checks the spectral characteristics of the reflected light from a measurement object obtained by irradiating the measurement object with light, against the spectral characteristics of the reflected light obtained by numerical analysis by modeling the measurement object, thereby estimating the periodic structure of the measurement object. Scatterometry includes a method using a library and a method without using a library. The library is a database in which the shapes of periodic structures and the spectral characteristics of beams of reflected light are accumulated in association with each other, and is created using an optical simulation such as rigorous coupled-wave analysis (RCWA). The spectral characteristics that best match the measured spectral characteristics are searched for in the library, and data of the shape of the periodic structure associated with the obtained spectral characteristics is determined as the shape of the measurement object. If a measurement object has a periodic structure, scatterometry can measure the shape of the measurement object with high accuracy.
The pattern formed by imprinting, however, does not necessarily have a periodic structure. If the shape of the pattern formed on the substrate does not have a periodic structure, the conventional method of measuring the thickness of a residual layer using scatterometry cannot measure the shape of the pattern with high accuracy.
Further, as a method of measuring the characteristics of a thin layer of a measurement object, ellipsometry is known. Ellipsometry is a technique capable of measuring the layer thickness of a measurement object by irradiating the measurement object with incident light and measuring the polarization state of the reflected light from the measurement object.
The conventional measurement using ellipsometry, however, does not measure the thickness of a residual layer in a recessed portion of a pattern formed by imprinting. Thus, it is not possible to measure with high accuracy the thickness of a residual layer in a recessed portion of a pattern formed by imprinting.